Vehicles are frequently equipped with vehicle telematics units that are capable of wirelessly communicating both voice and data between vehicles and central facilities. The central facilities may receive communications from vehicles via one or more monitored telephone numbers. When a vehicle attempts to communicate with a central facility, it dials a particular telephone number and a wireless carrier system can connect the vehicle with the central facility. Besides vehicle communications, the central facility may also be contacted by a number of other sources dialing the monitored telephone numbers. As a result, it can be challenging for the central facility to identify and service calls from vehicles while ignoring and/or preventing calls from other sources.